Re: [PATCH 4/5] PCI, acpiphp: add is_hotplug_bridge detection

[Bjorn Helgaas <bhelgaas@google.com>]

On Mon, Aug 20, 2012 at 8:35 AM, Jason Baron <jbaron@redhat.com> wrote:
> On Wed, Aug 15, 2012 at 01:36:43PM -0600, Bjorn Helgaas wrote:
>> On Tue, Jul 17, 2012 at 8:14 AM, Jason Baron <jbaron@redhat.com> wrote:
>> > On Wed, Jul 11, 2012 at 01:42:15PM -0600, Bjorn Helgaas wrote:
>> >> On Wed, Jul 11, 2012 at 11:14 AM, Jason Baron <jbaron@redhat.com> wrote:
>> >> > On Wed, Jul 11, 2012 at 09:50:19AM -0600, Bjorn Helgaas wrote:
>> >> >> On Sat, Jun 23, 2012 at 1:42 AM, Yinghai Lu <yinghai@kernel.org> wrote:
>> >> >> > When system support hotplug bridge with children hotplug slots, we need to make sure
>> >> >> > that parent bridge get preallocated resource so later when device is plugged into
>> >> >> > children slot, those children devices will get resource allocated.
>> >> >> >
>> >> >> > We do not meet this problem, because for pcie hotplug card, when acpiphp is used,
>> >> >> > pci_scan_bridge will set that for us when detect hotplug bit in slot cap.
>> >> >> >
>> >> >> > Reported-and-tested-by: Jason Baron <jbaron@redhat.com>
>> >> >> > Signed-off-by: Yinghai Lu <yinghai@kernel.org>
>> >> >> > Acked-by: Jason Baron <jbaron@redhat.com>
>> >> >> > ---
>> >> >> >  drivers/pci/hotplug/acpiphp_glue.c |   27 ++++++++++++++++++++++++++-
>> >> >> >  1 files changed, 26 insertions(+), 1 deletions(-)
>> >> >> >
>> >> >> > diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
>> >> >> > index ad6fd66..0f2b72d 100644
>> >> >> > --- a/drivers/pci/hotplug/acpiphp_glue.c
>> >> >> > +++ b/drivers/pci/hotplug/acpiphp_glue.c
>> >> >> > @@ -783,6 +783,29 @@ static void acpiphp_set_acpi_region(struct acpiphp_slot *slot)
>> >> >> >         }
>> >> >> >  }
>> >> >> >
>> >> >> > +static void check_hotplug_bridge(struct acpiphp_slot *slot, struct pci_dev *dev)
>> >> >> > +{
>> >> >> > +       struct acpiphp_func *func;
>> >> >> > +
>> >> >> > +       if (!dev->subordinate)
>> >> >> > +               return;
>> >> >> > +
>> >> >> > +       /* quirk, or pcie could set it already */
>> >> >> > +       if (dev->is_hotplug_bridge)
>> >> >> > +               return;
>> >> >> > +
>> >> >> > +       if (PCI_SLOT(dev->devfn) != slot->device)
>> >> >> > +               return;
>> >> >> > +
>> >> >> > +       list_for_each_entry(func, &slot->funcs, sibling) {
>> >> >> > +               if (PCI_FUNC(dev->devfn) == func->function) {
>> >> >> > +                       /* check if this bridge has ejectable slots */
>> >> >> > +                       if ((detect_ejectable_slots(func->handle) > 0))
>> >> >> > +                               dev->is_hotplug_bridge = 1;
>> >> >> > +                       break;
>> >> >> > +               }
>> >> >> > +       }
>> >> >> > +}
>> >> >> >  /**
>> >> >> >   * enable_device - enable, configure a slot
>> >> >> >   * @slot: slot to be enabled
>> >> >> > @@ -817,8 +840,10 @@ static int __ref enable_device(struct acpiphp_slot *slot)
>> >> >> >                         if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE ||
>> >> >> >                             dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
>> >> >> >                                 max = pci_scan_bridge(bus, dev, max, pass);
>> >> >> > -                               if (pass && dev->subordinate)
>> >> >> > +                               if (pass && dev->subordinate) {
>> >> >> > +                                       check_hotplug_bridge(slot, dev);
>> >> >>
>> >> >> I don't like this patch because it increases the differences between
>> >> >> the hotplug drivers, rather than decreasing them.
>> >> >>
>> >> >> For PCI Express devices, we set dev->is_hotplug_bridge in the
>> >> >> pci_setup_device() path (in set_pcie_hotplug_bridge()).  I think it
>> >> >> would make sense to try to expand that path to also handle SHPC and
>> >> >> ACPI hotplug as well.  ACPI is harder because it's not PCI-specified,
>> >> >> so we'd need some sort of pcibios or other optional hook.
>> >> >>
>> >> >> I don't have a clear picture of how this works -- if I understand
>> >> >> correctly, the situation is that we have a bridge managed by acpiphp.
>> >> >> That part makes sense because the bridge is on the motherboard and can
>> >> >> have a DSDT device.  Now we plug something into the slot below the
>> >> >> bridge.  I *think* this patch handles the case where this new
>> >> >> hot-added thing is also a bridge managed by acpiphp.  But where does
>> >> >> the ACPI device for this hot-added bridge come from?  It's an
>> >> >> arbitrary device the BIOS knows nothing about, so it can't be in the
>> >> >> DSDT.
>> >> >>
>> >> >
>> >> > So this came up while I was developing pci bridge hotplug for qemu.
>> >> > Currently, there is a top level host bus (with ACPI device definitions), where
>> >> > devices can be hot-plugged. What I've done is added a second level
>> >> > of hotplug pci busses (again with ACPI device definitions). Thus, we can
>> >> > now hotplug a bridge into the top-level bus and then devices behind it.
>> >> > Effectively increasing the hot-plug space from n -> n^2.
>> >> >
>> >> > Before the above pci patch, the devices behind the bridge would not
>> >> > configure their PCI BARs properly, since there were no i/o, mem resources
>> >> > assigned to the bridge. However, with the above patch in place things
>> >> > work as expected.
>> >> >
>> >> > Using the same code base I was able to do acpi hotplug on Windows 7,
>> >> > which correctly configured the both the bridge window and devices behind
>> >> > it on hot-plug. So currently, the above usage pattern works on Windows
>> >> > 7, but not on Linux.
>> >>
>> >> Thanks, Jason.  Do you have "lspci -v" output and the DSDT AML handy?
>> >> I'd like to look in more detail at what we're missing.
>> >
>> > Hi,
>> >
>> > Sorry for the delay...was on vacation.
>> >
>> > Anyways, below is the patch I have to the seabios acpi table. However,
>> > there are other pieces for seabios and qemu required. I still need to
>> > clean them up and send them out. But this pci patch (or something
>> > similar) is a required dependency.
>> >
>> > What 'lspci -v' output are you looking for?
>> >
>> > Let me know what else I can provide.
>>
>> Now it's my turn to be sorry for dropping this for so long :)
>>
>> I was thinking of the "lspci -v" output from your system (qemu guest)
>> and the disassembled DSDT extracted from the same system.  Then we
>> could talk about concrete devices and point to the corresponding
>> entries in lspci output and the ACPI namespace.
>
> Hi,
>
> posted to: http://people.redhat.com/~jbaron/bridge-hotplug/
>
> I've extracted the ssdt and dsdt tables.

Thanks, Jason.

I'd like to play with this on qemu myself so I don't have to ask so
many stupid questions.  Earlier you mentioned some other qemu and
seabios patches.  Are they usable yet?  I see the src/ssdt-pcihp.dsl
patch you posted Jul 17, but I think you were referring to some other
ones.

Bjorn